The present invention relates to an image forming apparatus having an image forming unit for printing image data input from a host device on a recording medium, in which developer is supplied to the image forming unit according to a specific control sequence.
In a conventional image forming apparatus such as a printer, a copier, a facsimile, and the likes, supply components such as an image supporting member, a charging unit, a developer supporting member, a developer supply unit, and a cleaning unit are disposed in an image forming unit. A developer container for supplying developer is detachably attached to the image forming unit.
In an integrated image forming unit, in which a plurality of image forming units in several colors is disposed in an integrated frame, a plurality of developer containers in several colors is independently and detachably attached to the integrated image forming unit. Only a developer container retaining a small amount of developer is replaced. The image forming units generally have a lifetime longer than that of the developer containers. Accordingly, the developer container is replaced several times during the lifetime of the image forming unit (refer to Patent Reference).    Patent Reference: Japanese Patent Publication No. 09-281770
In the conventional integrated image forming unit described above, when the image forming unit is replaced, if the developer container still retains a large amount of developer, it is necessary to discard a large amount of developer. Further, when the image forming unit is replaced while the developer container still retains a large amount of developer, developer may spill.
In view of the problems described above, an object of the present invention is to provide a medium transportation apparatus and an image reading apparatus, in which an amount of developer is controlled when an image forming unit is replaced. Accordingly, it is possible to reduce an amount of developer to be discarded when the image forming unit is replaced.
Further objects and advantages of the invention will be apparent from the following description of the invention.